JP2003525943A - Benzofuranone stabilization of phosphate esters - Google Patents

Abstract

A method for decolorizing and stabilizing alkylphenyl esters of phosphoric acid which comprises contacting the esters with an effective amount of a benzofuranone (e.g., is 5,7-di-t-butyl-3-(3,4 di-methylphenyl)3H-benzofuran-2-one) for a sufficient length of time to decolorize and stabilize the esters against subsequent color formation.

Description

Detailed Description of the Invention

[0001]

[Prior art]

Alkylphenyl esters of phosphoric acid are widely used as plasticizers in nitrocellulose and polyvinyl chloride (PVC) compositions. In addition, they are also used as additives for gasoline, functional fluids, oils, and are useful as flame retardants for plastics and the like.

The preparation of alkyl phenyl esters of phosphoric acid is usually carried out by phosphoryl chloride (POCl ₃
) Is added to a selected phenol such as cresol, xylenol, etc. and the resulting reaction mixture is gradually heated to about 180 ° C. The reaction is accelerated by the presence of Friedel-Crafts catalysts such as aluminum trichloride. In the conventional method, the reaction product is distilled under reduced pressure to remove unreacted phenol as the first fraction, and the alkylphenyl phosphate ester is isolated as the product fraction, and the high-boiling substance and the catalyst in the residue are isolated. Remains. The distilled product fraction is then thoroughly washed with sodium hydroxide solution to remove free phenol and acidic substances and then with water. The product fraction is generally treated with activated charcoal to remove materials that cause coloration.

[0003]

[Problems to be Solved by the Invention]

This method works very well for the conventional preparation of esters from by-product alkylphenols, but when applied to a mixture of alkylphenols obtained by alkylating phenols with olefins, it does not give satisfactory materials. . It was found to color when the product was exposed to air or heat or stored in the dark. This coloration is attributed to the presence of di (o-alkyl) phenol in the alkylated phenol. The steric inhibition by the two ortho substituents on the 2,6-dialkylphenols and the 2,4,6-trialkylphenols makes the washing with sodium hydroxide solution less effective on the phenols, so that they are sodium hydroxide. Not removed by washing.

These so-called “hindered phenols” are oxidized in air to form highly colored quinones, which are the undesired source of coloration of the product. The quinone is
Decolorized to some extent by light, but reappears when stored in the dark. The color can be strong when the ester is mixed or kneaded with polyvinyl chloride (PVC) under the influence of air and heat.

Thus, for example, in the case of 2,6-diisopropylphenol, the corresponding diphenoquinones or benzoquinones are highly colored. Esters made from alkylated phenol mixtures include di-orthoalkylphenols such as 2,6-diisopropylphenol and may be too highly colored for many applications, especially as a plasticizer. Highly colored phosphate esters have limited utility for plasticizer applications and have poor market value.

US Pat. No. 3,681,482 discusses the coloring mechanism of phosphate esters, which relates the degree of coloring of phosphate esters with the degree of alkyl substitution on the aromatic ring. Therefore, tris (methylphenyl) phosphate is less colored than tris (dimethylphenyl) phosphate. This is because tris (methylphenyl) phosphate has the aromatic ring replaced by only one methyl group, while tris (dimethylphenyl) phosphate has
It can be explained that it is more colored because the aromatic ring is substituted by two methyl groups.

Many methods have been proposed to solve the undesirable color formation. For example,
U.S. Pat. No. 1,958,210 discloses the removal of decolorizable and oxidizable impurities from phosphate esters using activated carbon. This method is not satisfactory because activated carbon is not an effective decolorizing agent for alkylphenyl phosphate esters. In some cases, for example the decolorization of isopropyl phenyl diphenyl phosphate esters, the use of activated carbon may increase the coloration.

US Pat. No. 2,113,951 describes alkylphenols such as cresylic acid in sulfuric acid,
Disclosed is a method of distilling and purifying in the presence of a mineral acid such as hydrochloric acid or phosphoric acid. Purified cresylic acid is used in the production of tricresyl phosphate ester,
It is said to be more stable to the effects of heat and light than the corresponding esters made from alkylphenols distilled in the absence of inorganic acids. The disadvantage of this method is that the phenolic residues are oxidized to colored quinones and must be thoroughly distilled to remove them and prevent further coloring.

Another color reduction method is proposed in US Pat. No. 3,681,482 in which a tris (alkylphenyl) phosphate ester containing 2,6-diisopropylphenol and the corresponding diphenoquinone is permanently decolorized. And sodium borohydride is used for color stabilization. Sodium borohydride reduces diphenoquinone to colorless 2,6-diisopropylphenol, which remains in the product, causing the purified product to discolor if exposed to oxidizing conditions. Sodium borohydride treatment is also an expensive material and requires several hours to overnight treatment time.

Thus, the methods proposed in the above-mentioned prior art documents have been found to be industrially ineffective for removing color from alkylphenol esters of phosphoric acid, and these esters are used as PVC plasticizers. The stability in the PVC mill is not improved.

Other attempts to solve this problem use many other substances as additives for decolorization of the composition. Examples of additives include: Hydrazine (US Pat.
3,852,288); soluble nitrilotriacetate salts (US Pat. No. 3,931,360)
Certain sodium salts (US Pat. No. 3,931,361); oxidizable nitrogen compounds (US Pat. No. 3,931,362); triorganoaluminum compounds and their hydrides (US Pat. No. 3,931,363). ); Phosphite ester (US Pat. No. 3,931,364); Water-soluble salt of reduced sulfur (US Pat. No. 3
, 931,365); in situ addition of phosphorus trichloride (US Pat. No. 3,931,366); tin salts of fatty acids (US Pat. No. 3,931,367); and oxygenated thiourea (US Pat. No. 4,263,232). Specification).

[0012]

[Means for Solving the Problems]

The present invention is a method for stabilizing and decolorizing phosphate esters with benzofuranone additives.

[0013]

DETAILED DESCRIPTION OF THE INVENTION

A method of permanently removing color from a colored phosphate ester according to the method of the present invention comprises contacting the phosphate ester with an effective amount of a benzofuranone additive for a time sufficient to reduce the color to the desired level, thereby This is accomplished by decolorizing the ester and stabilizing it for subsequent color formation. A preferred benzofuranone additive for use in the present invention is 5,7-di-t-butyl-3- (3,
4-dimethylphenyl) 3H-benzofuran-2-one, with a CAS number of 1813
14-48-7. It is marketed by Ciba Additives under the trade name "HP-136".

The process of the invention is applicable to all phosphate esters made from alkylated phenol mixtures containing hindered phenols, for example those having alkyl groups in both ortho positions of the hydroxyl groups. The ester may contain 0.5 to 3 alkylaryl groups and 0 to 2.5 phenyl groups.

Preferably, the triaryl phosphate ester treated by the method of the present invention contains 1-2 alkaryl groups. The ester corresponds to the general formula: ## STR3 ## where the formula is embedded below, where R is alkylaryl and R ₁ and R ₂ are alkyl, alkaryl, aralkyl or aryl, where the alkyl is 1 to 20 groups,
More preferably it can contain from 1 to 12 carbon atoms. There may be some triphenyl phosphate present.

Alkylated phenols, including hindered phenols, typically include phenols derived from C ₁ -C ₁₂ unsaturated hydrocarbons such as ethylene, propylene, isobutylene and its isomers, amylene and its isomers, tripropylene, tetrapropylene, Decene,
It is obtained by alkylation with dodecene, diisobutylene and the like. Typical examples of alkyl radicals are: methyl, ethyl, normal propyl, isopropyl, normal butyl, isobutyl, secondary butyl, tertiary butyl, normal amyl, isoamyl, 2-methylbutyl, 2,2-dimethylpropyl, 1 -Methylbutyl, diethylmethyl, 1,2-dimethylpropyl, tertiary amyl, normalhexyl, 1-methylamyl, 1-ethylbutyl, 1,2,2-trimethylpropyl, 3,3-dimethylbutyl, 1,1,2- Trimethylpropyl, 2-methylamyl, 1,1-dimethylbutyl, 1-ethyl-2-methylpropyl, 1,3-dimethylbutyl, isohexyl, 3-methylamyl, 1,2-dimethylbutyl, 1-methyl-1-ethyl Propyl, 2-ethyl, normal heptyl, 1,1,2,3-tetramethylpropyl, 1,2-dimethyl-1-ethylpropyl, 1,1,2-trimethylbutane 1-isopropyl-2-methylpropyl, 1-methyl-2-ethylbutyl, 1,1-diethylpropyl, 2-methylhexyl, 1,1-dimethylamyl, 1-isopropylbutyl, 1-ethyl-3-methylbutyl , 1
, 4-Dimethylamyl, isoheptyl, 1-methyl-1-ethylbutyl, 1-ethyl-2-methylbutyl, 1-methylhexyl, 1-1-propylbutyl, normaloctyl, 1-methylheptyl, 1,1-diethyl- 2-methylpropyl, 1,1,3,3-tetramethylbutyl, 1,1-diethylbutyl, 1,1-dimethylhexyl, 1-methyl-1-ethylamyl, 1-
Methyl-1-propylbutyl, 2-ethylhexyl, 6-methylheptyl, normalnonyl, 1-methyloctyl, 1-ethylheptyl, 1,1-dimethylheptyl, 1-ethyl
-1-propylbutyl, 1,1-diethyl-3-methylbutyl, diisobutylmethyl-3,5,5
-Trimethylhexyl, 3,5-dimethylheptyl, normaldecyl, 1-propylheptyl, 1,1-diethylhexyl, 1,1-dipropylbutyl, 2-isopropyl-5-methylhexyl and C ₁₁ -C ₂₀ alkyl groups . Further included are aralkyl groups such as benzyl, alpha- or beta-phenylethyl, alpha, alpha-dimethylbenzyl and the like. Also included are cyclohexyl, cycloheptyl, cyclododecyl and the like. Typical examples of aryl and alkaryl radicals are phenyl, cresyl, xylyl, alkoxylated phenyl, isopropylphenyl, butylphenyl, alpha-alkylbenzylphenyl and alpha, alpha-dialkylbenzylphenyl such as alpha-methylbenzylphenyl, alpha, alpha. Examples thereof include dimethylbenzylphenyl, tert-nonylphenylamylphenyl, tert-butylphenyl, isooctylphenyl, dodecylphenyl, tert-octylphenyl and the like.

The preparation of the ester according to the invention is carried out, for example, by alkylating phenol with an olefin and then adding POCl ₃ . These alkylated phenols yield esters similar to the traditional by-products, cresylic acid from coal tar or methylphenol. Esters are generally prepared by reacting an alkylphenol with POCl _{3 in} the presence of a Friedel-Crafts catalyst at elevated temperature, typically 180 ° C., until HCl evolution ceases and the reaction is complete. To be The reaction mixture is then heated to distill excess phenol as overhead effluent. Thereafter, the temperature and / or the degree of vacuum is increased and the phosphate ester product is distilled leaving behind catalyst and a small amount of high boiling distillation residue.

Conventionally, the ester product is washed with aqueous alkali to remove free phenol present in the range of multiples of about 0.1%. The washed product is separated from the water, usually treated with activated carbon and filter aids such as diatomaceous earth and filtered.
However, in the presence of air and heat, hindered phenol discoloration of the product can occur later, resulting in a product that is unsuitable for applications where colorlessness is important.

In accordance with the present invention, the phosphate ester product is the isolated alkyl phosphate ester product, as described above, in an effective amount of benzofuranone additive,
Decolorization and color stabilization treatment is carried out by contacting until the color is appropriately reduced. US Pat. No. 5,516,920, entitled "3-Arylbenzofuranones," is incorporated herein in its entirety to describe the types of benzofuranones that can be used in accordance with the present invention.

Treatment times generally vary from about 5 minutes to about 24 hours depending on the amount of phosphate ester treated, the amount and concentration of the benzofuranone additive selected for use, temperature, stirring and the like. Preferably, the phosphate ester is washed for about 1 hour to about 5 hours at about 20 ° C to 100 ° C. More preferably, the treatment is performed at about 45 ° C to 70 ° C.

The amount of benzofuranone used can vary between about 1 ppm and about 2% by weight of the phosphate ester treated. Higher amounts of benzofuranone can be used, but this does not provide any benefit. It is preferred to use an amount of about 5 ppm to about 0.1% by weight of the phosphate ester. In a given case, the amount of soluble benzofuranone used is influenced by many factors, including the amount of color present, the degree of color improvement desired, the type of phosphate ester processed, the processing time, etc. It

The method of the present invention is generally carried out under atmospheric pressure. However, higher or lower pressures may also be used. It may be carried out in an inert atmosphere, for example, under nitrogen capable of suppressing reoxidation.

[0023]   The process of the invention may be carried out batchwise or continuously.

An advantage of the present invention is that after treatment of the phosphate ester with the benzofuranone additive, no additional steps or special treatments are required except for optional washing steps, phase separation steps and drying steps. Is. Traces of residual benzofuranone, if present, do not adversely affect the industrial properties of the phosphate ester.

[0025]

【Example】

The methods disclosed above are further described in the following examples, which are not intended to limit the invention thereto. Throughout the examples and the specification, all parts and percentages are by weight unless otherwise stated.

Example 1 In this example, a phosphate ester sample (PHOSFLEX 31L) was treated with various amounts of a lactone-based stabilizer (HP 136) to determine the color stability of the treated one. Accelerated color stability measurements were carried out in a closed sample bottle at 80 ° C for 28 hours. The results of this test are shown in Table 1. As you can see from this measurement, 10
In the concentration range of ˜50 ppm (weight), the stabilizer is effective for decolorizing and stabilizing the phosphate ester. The samples tested without additives under the same conditions exhibited a pronounced color, i.e. more than 300 APHA colors. The color at the start of the test for this sample was approximately 50 APHA.

[Table 1] Table 1. Results of stabilization tests at additive concentrations of 10 to 50 ppm. The test was conducted at 80 ° C. for 28 hours.

Example 2 In this example, a phosphate ester sample (PHOSFLEX 21L) was treated with various amounts of a lactone-based stabilizer (HP 136) to determine the color stability of the treated one. Accelerated color stability measurements were carried out in a closed sample bottle at 80 ° C for 28 hours. The results of this test are shown in Table 2. As you can see from this measurement, 10
In the concentration range of ˜50 ppm (weight), the stabilizer is effective for decolorizing and stabilizing the phosphate ester. Samples tested without additives under the same conditions exhibited a noticeable color,> 300 APHA colors. The color at the start of the test for this sample is approximately 5
It was 0 APHA.

[Table 2] Table 2. Results of stabilization tests at additive concentrations of 10 to 50 ppm. The test was conducted at 80 ° C. for 28 hours.

Example 3 In this example, a phosphate ester sample (PHOSFLEX 21L) was added to about 100 ppm.
Was treated with the lactone-based stabilizer (HP 136), and the color stability of the treated product was determined. Accelerated color stability measurements were carried out in a closed sample bottle at 80 ° C for 28 hours. At this concentration of stabilizer, the color of the sample is about 200 APHA to about 25 APH.
Reduced to A. Under the above test conditions, the treated material was stable at this level of color for a longer period of time. This clearly shows that the lactone additive is both effective in reducing the color of the material and stabilizing it against color formation.

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Desikan, Anansa             New York, USA 10566,             Peak Skill, 2 Hendrick Hills             (No address) (72) Inventor Abramson, Alan             36608, Alabama, United States             -Veil, 106 sea du dora             Eve (no address) F-term (reference) 4H050 AA02 AD40 BB61

Claims (8)

[Claims] 1. An alkylphenyl ester of phosphoric acid is contacted with an effective amount of a benzofuranone additive for a time sufficient to reduce the color to the desired level, thereby decolorizing the ester and for subsequent color formation. A method for decolorizing an alkyl phenyl ester of phosphoric acid, which comprises being stabilized. 2. The alkyl phenyl ester corresponds to the formula:
The method described. (In the above formula, R is alkaryl and R ₁ and R ₂ are selected from the group consisting of alkyl, aralkyl, alkaryl, and aryl, wherein the alkyl group contains from 1 to about 20 carbon atoms. .) 3. The method of claim 2, wherein the alkyl group contains 1 to about 12 carbon atoms. 4. The method of claim 1 wherein the alkyl phenyl ester comprises unreacted substituted and unsubstituted phenol. 5. Benzofuranone is 5,7-di-t-butyl-3- (3,4-di-methylphenyl) 3.
The method according to claim 1, which is H-benzofuran-2-one. 6. The method according to claim 1, wherein the decolorization and stabilization are performed under an inert atmosphere. 7. The method of claim 6, wherein the inert atmosphere comprises nitrogen. 8. The method of claim 1, wherein the alkyl phenyl ester of phosphoric acid is isopropyl phenyl phenyl phosphate.